Will He Kill Her?

I have two roosters. My dominant rooster will be going to a new home. I have a huge barred rock rooster that I'm keeping to breed. Right now he's submissive and never crowed, but I suspect that'll change once my dominant roo is gone. But, I also have a little frizzle bantam and she's currently in a run, not with the others. I would love to let her out, but I'm concerned he'll mount her and his weight alone will kill her or at least break her legs. Thoughts?